This invention relates to automatic control of an oscillatory penetration apparatus. In particular, the invention relates to systems and methods for control of sonic drilling.
Sonic drilling (rotary, vibratory drilling) is an advanced drilling technique that offers great advantages for obtaining the relatively undisturbed core samples that are needed to gather subterranean environmental data. In addition, sonic drilling uses a unique method for the minimization, or even elimination, of the use of drilling fluids and the production of cuttings that are brought to the surface as ground penetration occurs. However, the sonic drilling process is highly complex and, as such, requires unique and advanced operator skills. Moreover, the depths to which background art sonic drilling techniques can be used are limited, with practical drilling depths not exceeding about 1,000 to 1,500 feet.
Efficient application of sonic drilling is realized by sustaining the drill string at resonance throughout the entire drilling process. This task is complicated by the fact that there is a strong coupled relationship between the frequency of the sonic driver, or drill head, and the forces applied (magnitude and direction) to the drill string by: (1) the sonic drill bit; (2) the weight of the drill string, which changes as more depth is achieved; and (3) the resistance to penetration imposed by both the side-load (lateral) forces of the drilled material (e.g., soil) and the resistance to penetration at the drill bit. All of these factors are coupled (interrelated) and must be kept in the proper relationship to keep the drill string in resonance to ensure peak performance. This complex relationship affects the power utilization efficiency, as well as the ability of the drill string to penetrate the earth. In addition, the collective factors affecting drill string penetration are also a function of both drilling process conditions and subterranean geophysical conditions.
Because of these complex and coupled issues, current sonic drilling technology requires highly trained operators to directly control driving frequency, power input and the constant push or pull force applied to the drill string. However, because of the complexity of coupled factors, and lack of information (measurements of drill string performance), even the most skilled technicians cannot obtain optimal performance from background art sonic drilling equipment. In fact, measures that must be taken to fully achieve maximum performance and efficiency in sonic drilling are counterintuitive, and, hence, are not even implemented by skilled operators. As such, there is a compelling need for an automated control system that maintains the drill string at an optimal sonic drilling condition.
The need for an automated sonic drilling control has been identified, and efforts to provide automated control have been attempted, but have been unsuccessful. However, it is significant to note that these previous efforts have not been attempted using a fundamental understanding of the parameters involved, both physically or analytically. Hence, the goal of developing a much-needed, automated drilling methodology for sonic drilling was heretofore unachievable. What has been needed is a technology that is based on a fundamental understanding of the physics of the resonant system, from which dynamic analytical models to use in quantifying all aspects the resonant system may be assembled.
The background art is characterized by U.S. Pat. Nos. 2,911,192; 2,975,846; 3,004,389; 3,375,884; 3,379,263; 3,461,979; 3,477,237; 3,572,139; 3,633,688; 3,736,843; 3,741,315; 4,330,156; 4,384,625; 4,693,325; 4,836,299; 4,527,637; 5,141,061; 5,417,290; 5,540,295; 5,549,170; 5,562,169; 6,129,159; 6,736,209; 6,863,136; 7,191,852; 7,234,537; and 7,341,116; and U.S. Patent Application No. 2007/289,778; the disclosures of which patents and patent application are incorporated by reference as if fully set forth herein. The background art is also characterized by WO01/83933.